Bob, that's a good collection of links. I'd read Evans article on the laser for flatness and skimmed the circuit cellar article. I really like the idea of a a diy linear encoder, I think it would be well received and have lots of applications. On my last electronics order i bought some hall sensors to play around the ball bearing (newall) idea, but haven't progress more than assigning a parts drawer.
didn't realize the circuit cellar one was that accurate, but if its delivering .0001 that's awesome. Thanks for compiling the list and providing some mental stretch - when can we see a prototype
